Rear plate for plasma display panel

ABSTRACT

Disclosed is a rear plate of a plasma display panel. In the rear plate, a dielectric layer or a barrier wall layer is formed by forming slurry in a tape of a green tape and then attaching the green tape to upper surfaces of electrodes and a glass substrate. Therefore, a PDP employing a rear plate according to the present invention has superior electric and optical characteristics.

TECHNICAL FIELD

The present invention relates to a rear plate of a plasma display panel.

BACKGROUND ART

As generally known in the art, a plasma display panel (PDP) is a displaydevice having a front glass substrate and a rear glass substrate betweenwhich a discharge space is formed, so that plasma discharge may generatein the discharge space, thereby causing phosphors in the discharge spaceto be excited and emit light, so as to display a screen. In comparisonwith liquid crystal panel, the PDP can display an image at a higherspeed and can easily realize a larger screen. Therefore, PDPs areemployed in a field of a television with a higher quality and a largerscreen.

Hereinafter, an AC PDP, which is currently the mainstream of PDPs, willbe described.

A PDP includes a front plate and a rear plate assembled in parallel witheach other. The front plate includes a front glass substrate, aplurality of discharge sustaining electrodes formed on a lower surfaceof the front glass substrate, bus electrodes formed on lower surfaces ofthe discharge sustaining electrodes, a dielectric layer covering thedischarge sustaining electrodes and the bus electrodes, and a protectionlayer formed on a lower surface of the dielectric layer. Further, therear plate includes a rear glass substrate, address electrodes formed onan upper surface of the rear glass substrate, a dielectric layer formedon upper surfaces of the address electrodes, barrier walls formed on anupper surface of the dielectric layer to form discharge cells, andphosphorous layers formed on surfaces of the barrier walls. Herein, twodischarge sustaining electrodes are disposed in each discharge cell.

Therefore, the address electrodes and discharge sustaining electrodescause discharge in the discharge cells, and ultraviolet rays generatedby the discharge excites the phosphorous layer, which then emits visiblerays, thereby forming a desired image on a screen.

In general, in forming barrier walls of a rear plate of a PDP, thebarrier walls are preliminary formed and are then baked, as disclosed inJapanese Patent Laid-Open Nos. P9-283018 and P9-102275.

When a PDP has been manufactured by attaching a conventional rear plateas described above to a front plate, the PDP has deteriorated electricaland optical properties due to characteristics of the manufacturingmethod thereof.

DISCLOSURE OF THE INVENTION

Therefore, the present invention has been made in view of theabove-mentioned problems, and it is an object of the present inventionto provide a rear plate of a plasma display panel, which can improveelectric and optical characteristics of a PDP.

According to an aspect of the present invention, there is provided arear plate of a plasma display panel, the rear plate comprising: a glasssubstrate; electrodes formed in a shape of patterns on an upper surfaceof the glass substrate; a dielectric layer formed on upper surfaces ofthe electrode and the upper surface of the glass substrate; barrierwalls formed in a shape of a pattern through etching on an upper surfaceof the dielectric layer; and phosphorous layers formed on side surfacesand bottom surfaces of the barrier walls, wherein: each of theelectrodes has a thickness of 2 to 8 μm and a specific resistance of1.0×10⁻⁶ to 5.0×10⁻⁶ Ωcm; the dielectric layer is made from a firstmixture which includes a first filler and at least one glass powderselected from among a first glass powder and a second glass powder, thefirst glass powder including PbO of 30 to 80 wt %, ZnO of 0 to 20 wt %,SiO₂ of 0 to 20 wt %, B₂O₃ of 5 to 40 wt %, Al₂O₃ of 0 to 12 wt %,Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0 to 5 wt %, thesecond glass powder including Bi₂O₃ of 36 to 84 wt %, B₂O₃ of 5 to 28 wt%, PbO of 0 to 46 wt %, ZnO of 0 to 30 wt %, Al₂O₃ of 0 to 13 wt %, SiO₂of 0 to 10 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0to 3 wt %, each of the first and second glass powders having an averageparticle diameter of 1 to 10 μm, a softening temperature of 390 to 550°C., and a thermal expansive coefficient of 63×10⁻⁷ to 83×10⁻⁷/° C., thefirst filler having an average particle diameter of 0.01 to 10 μm, thedielectric layer having a dielectric constant of 8 to 20, a reflectanceof 50 to 80%, an etching rate of 0.01 to 1.0 μm/min with respect toinorganic acid, and a thickness of 10 to 30 μm; the barrier walls aremade from a second mixture which includes a second filler, organicmaterial, additives, and at least one glass powder selected from thegroup consisting of a third, fourth, and fifth glass powders, the thirdglass powder including ZnO of 0 to 48 wt %, SiO₂ of 0 to 21 wt %, B₂O₃of 25 to 56 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 38 wt %,and BaO+CaO+MgO+SrO of 0 to 15 wt %, the fourth glass powder includingPbO of 25 to 65 wt %, ZnO of 0 to 35 wt %, SiO₂ of 0 to 26 wt %, B₂O₃ of0 to 30 wt %, Al₂O₃+SnO₂ of 0 to 13 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %,BaO of 0 to 26 wt %, and CaO+MgO+SrO of 0 to 13 wt %, the fifth glasspowder including PbO of 35 to 55 wt %, B₂O₃ of 18 to 25 wt %, ZnO of 0to 35 wt %, BaO of 0 to 16 wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9 wt %,CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %, andCaO+MgO+SrO of 0 to 13 wt %, the third glass powder having a softeningtemperature of 460 to 630° C., a thermal expansive coefficient of64×10⁻⁷ to 105×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, each of the fourth and fifth glass powders having a softeningtemperature of 390 to 550° C., a thermal expansive coefficient of63×10⁻⁷ to 110×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, the second filler having an average particle diameter of 0.01 to 10μm, the barrier walls being formed with a height of 100 to 180 μm byattaching a barrier wall layer formed in a shape of green tapes to anupper surface of the dielectric layer, firing the barrier wall layertogether with the dielectric layer at a temperature between 400° C. and700° C., and then etching the barrier wall layer, the barrier wall layerhaving a dielectric constant of 5 to 18, a reflectance of 40 to 80%, anetching rate of 1.0 to 50.0 μm/min with respect to inorganic acid; eachof the phosphorous layers has a thickness of 10 to 50 μm; and adifference between the thermal expansive coefficients of the dielectriclayer and the barrier wall layer has a percentage between 0 and 10%, anda difference between the softening temperatures of the dielectric layerand the barrier wall layer has a value between 0 and 20° C.

According to another aspect of the present invention, there is provideda rear plate of a plasma display panel, the rear plate comprising: aglass substrate; electrodes formed in a shape of patterns on an uppersurface of the glass substrate; a dielectric layer formed on uppersurfaces of the electrode and the upper surface of the glass substrate;barrier walls formed in a shape of a pattern through etching on an uppersurface of the dielectric layer; and phosphorous layers formed on sidesurfaces and bottom surfaces of the barrier walls, wherein: each of theelectrodes has a thickness of 2 to 8 μm and a specific resistance of1.0×10⁻⁶ to 5.0×10⁻⁶ Ωcm; the dielectric layer is made from a firstmixture which includes a first filler, organic material, additives, andat least one glass powder selected from among a first glass powder and asecond glass powder, the first glass powder including PbO of 30 to 80 wt%, ZnO of 0 to 20 wt %, SiO₂ of 0 to 20 wt %, B₂O₃ of 5 to 40 wt %,Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrOof 0 to 5 wt %, the second glass powder including Bi₂O₃ of 36 to 84 wt%, B₂O₃ of 5 to 28 wt %, PbO of 0 to 46 wt %, ZnO of 0 to 30 wt %, Al₂O₃of 0 to 13 wt %, SiO₂ of 0 to 10 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, andBaO+CaO+MgO+SrO of 0 to 3 wt %, each of the first and second glasspowders having an average particle diameter of 1 to 10 μm, a softeningtemperature of 390 to 550° C., and a thermal expansive coefficient of63×10⁻⁷ to 83×10⁻⁷/° C., the first filler having an average particlediameter of 0.01 to 10 μm, the dielectric layer having a dielectricconstant of 8 to 20, a reflectance of 50 to 80%, an etching rate of 0.01to 1.0 μm/min with respect to inorganic acid, and a thickness of 10 to30 μm, the dielectric layer being formed in a shape of a green tape andthen attached to upper surfaces of the electrodes; the barrier walls aremade from a second mixture which includes a second filler, organicmaterial, additives, and at least one glass powder selected from thegroup consisting of a third, fourth, and fifth glass powders, the thirdglass powder including ZnO of 0 to 48 wt %, SiO₂ of 0 to 21 wt %, B₂O₃of 25 to 56 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 38 wt %,and BaO+CaO+MgO+SrO of 0 to 15 wt %, the fourth glass powder includingPbO of 25 to 65 wt %, ZnO of 0 to 35 wt %, SiO₂ of 0 to 26 wt %, B₂O₃ of0 to 30 wt %, Al₂O₃+SnO₂ of 0 to 13 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %,BaO of 0 to 26 wt %, and CaO+MgO+SrO of 0 to 13 wt %, the fifth glasspowder including PbO of 35 to 55 wt %, B₂O₃ of 18 to 25 wt %, ZnO of 0to 35 wt %, BaO of 0 to 16 wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9 wt %,CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %, andCaO+MgO+SrO of 0 to 13 wt %, the third glass powder having a softeningtemperature of 460 to 630° C., a thermal expansive coefficient of64×10⁻⁷ to 105×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, each of the fourth and fifth glass powders having a softeningtemperature of 390 to 550° C., a thermal expansive coefficient of63×10⁻⁷ to 110×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, the second filler having an average particle diameter of 0.01 to 10μm, the barrier walls being formed with a height of 100 to 180 μm byattaching a barrier wall layer formed in a shape of green tapes to anupper surface of the dielectric layer, firing the barrier wall layertogether with the dielectric layer at a temperature between 400° C. and700° C., and then etching the barrier wall layer, the barrier wall layerhaving a dielectric constant of 5 to 18, a reflectance of 40 to 80%, andan etching rate of 1.0 to 50.0 μm/min with respect to inorganic acid;each of the phosphorous layers has a thickness of 10 to 50 μm; and adifference between the thermal expansive coefficients of the dielectriclayer and the barrier wall layer has a percentage between 0 and 10%, anda difference between the softening temperatures of the dielectric layerand the barrier wall layer has a value between 0 and 20° C.

According to still another aspect of the present invention, there isprovided a rear plate of a plasma display panel, the rear platecomprising: a glass substrate; electrodes formed in a shape of patternson an upper surface of the glass substrate; a dielectric layer formed onupper surfaces of the electrode and the upper surface of the glasssubstrate; barrier walls formed in a shape of a pattern through etchingon an upper surface of the dielectric layer; and phosphorous layersformed on side surfaces and bottom surfaces of the barrier walls,wherein: each of the electrodes has a thickness of 2 to 8 μm and aspecific resistance of 1.0×10⁻⁶ to 5.0×10⁻⁶ Ωcm; the dielectric layer ismade from a first mixture which includes a first filler, organicmaterial, additives, and at least one glass powder selected from among afirst glass powder and a second glass powder, the first glass powderincluding PbO of 30 to 80 wt %, ZnO of 0 to 20 wt %, SiO₂ of 0 to 20 wt%, B₂O₃ of 5 to 40 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 5wt %, and BaO+CaO+MgO+SrO of 0 to 5 wt %, the second glass powderincluding Bi₂O₃ of 36 to 84 wt %, B₂O₃ of 5 to 28 wt %, PbO of 0 to 46wt %, ZnO of 0 to 30 wt %, Al₂O₃ of 0 to 13 wt %, SiO₂ of 0 to 10 wt %,Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0 to 3 wt %, eachof the first and second glass powders having an average particlediameter of 1 to 10 μm, a softening temperature of 390 to 550° C., and athermal expansive coefficient of 63×10⁻⁷ to 83×10⁻⁷/° C., the firstfiller having an average particle diameter of 0.01 to 10 μm, thedielectric layer having a dielectric constant of 8 to 20, a reflectanceof 50 to 80%, an etching rate of 0.01 to 1.0 μm/min with respect toinorganic acid, and a thickness of 10 to 30 μm, the dielectric layerbeing formed in a shape of a green tape; the barrier walls are made froma second mixture which includes a second filler, organic material,additives, and at least one glass powder selected from the groupconsisting of a third, fourth, and fifth glass powders, the third glasspowder including ZnO of 0 to 48 wt %, SiO₂ of 0 to 21 wt %, B₂O₃ of 25to 56 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 38 wt %, andBaO+CaO+MgO+SrO of 0 to 15 wt %, the fourth glass powder including PbOof 25 to 65 wt %, ZnO of 0 to 35 wt %, SiO₂ of 0 to 26 wt %, B₂O₃ of 0to 30 wt %, Al₂O₃+SnO₂ of 0 to 13 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %,BaO of 0 to 26 wt %, and CaO+MgO+SrO of 0 to 13 wt %, the fifth glasspowder including PbO of 35 to 55 wt %, B₂O₃ of 18 to 25 wt %, ZnO of 0to 35 wt %, BaO of 0 to 16 wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9 wt %,CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %, andCaO+MgO+SrO of 0 to 13 wt %, the third glass powder having a softeningtemperature of 460 to 630° C., a thermal expansive coefficient of64×10⁻⁷ to 105×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, each of the fourth and fifth glass powders having a softeningtemperature of 390 to 550° C., a thermal expansive coefficient of63×10⁻⁷ to 110×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, the second filler having an average particle diameter of 0.01 to 10μm; each of the phosphorous layers has a thickness of 10 to 50 μm; and adifference between the thermal expansive coefficients of the dielectriclayer and the barrier wall layer has a percentage between 0 and 10%, anda difference between the softening temperatures of the dielectric layerand the barrier wall layer has a value between 0 and 20° C., wherein abarrier wall layer formed in a shape of green tapes, which has adielectric constant of 5 to 18, a reflectance of 40 to 80%, and anetching rate of 1.0 to 50.0 μm/min with respect to inorganic acid, isintegrated with the dielectric layer to form a lamination of dielectriclayer/barrier wall layer, and the lamination of dielectric layer/barrierwall layer is attached to the upper surfaces of the electrodes and theglass substrate, is baked at a temperature between 400° C. and 700° C.,and is then etched, so that the barrier walls are formed with a heightof 100 to 180 μm.

Herein, each of the barrier walls has at least two different layershaving different etching rates with respect to inorganic acid.

In a rear plate of a plasma display panel according to the presentinvention, a dielectric layer or a barrier wall layer is formed byforming slurry in a tape of a green tape and then attaching the greentape to upper surfaces of electrodes and a glass substrate. Therefore, aPDP employing a rear plate according to the present invention hassuperior electric and optical characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a sectional view of a rear plate of a plasma display panelaccording to a first embodiment of the present invention;

FIG. 2 is a sectional view of a rear plate of a plasma display panelaccording to a second embodiment of the present invention; and

FIG. 3 is a sectional view of a rear plate of a plasma display panelaccording to a third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a rear plate of a plasma display panel according topreferred embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a rear plate of a plasma display panelaccording to a first embodiment of the present invention.

As shown in FIG. 1, a rear plate 100 of a plasma display panel(hereinafter, referred to as “PDP”) according to the present embodimentincludes a glass substrate 110, electrodes 120 formed in a shape of apattern and spaced at a predetermined interval from each other on anupper surface of the glass substrate 110, a dielectric layer 130 formedon upper surfaces of the electrode 120 and the upper surface of theglass substrate 110, barrier walls 140 formed on an upper surface of thedielectric layer 130 and spaced a predetermined interval from eachother, and phosphorous layers 150 formed on side surfaces and bottomsurfaces of the barrier walls 140.

Since the barrier walls 140 is formed through etching, the barrier wallsmust have a proper etching rate for etching solution and the electrodes120 and the dielectric layer 130 must have resistance to the etchingsolution. In order to meet the requirements described above, each of thefunctional layers of the rear plate 100 according to the presentembodiment has a specific composition, which will be describedhereinafter.

First Embodiment

In the rear plate 100 according to the first embodiment of the presentinvention, the dielectric layer 130 is formed by a screen printingmethod, the barrier walls are formed in a shape of green tapes, and thenthe dielectric layer 130 and the barrier walls are simultaneously baked.This process will be described in detail hereinafter.

The electrodes 120 formed on the upper surface of the glass substratehas a thickness of 2˜8 μm. That is, photosensitive paste for theelectrodes, which has a specific resistance of 2.5×10⁻⁶ to 4.0×10⁻⁶ Ωcm,is screen-printed on the upper surface of the glass substrate 110, isdried, and is then subjected to photolithography and firing, therebyforming the electrodes 120. When the electrodes have a specificresistance of lower than 2.5×10⁻⁶, the low resistance enables theelectrodes to process an address signal without noise. However, theelectrodes must be made from gold or silver with high purity, whichincreases the manufacturing cost for the electrodes. In contrast, whenthe electrodes have a specific resistance of larger than 4×10⁻⁶ Ωcm,such problems as increase of an address driving voltage are caused.

The dielectric layer 130 is made from mixture of a first filler and atleast one glass powder selected from among a first glass powder and asecond glass powder. The dielectric layer 130 has a thickness of 10 to30 μm.

The first glass powder comprises PbO of 30 to 80 wt %, ZnO of 0 to 20 wt%, SiO₂ of 0 to 20 wt %, B₂O₃ of 5 to 40 wt %, Al₂O₃ of 0 to 12 wt %,Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0 to 5 wt %. Thesecond glass powder comprises Bi₂O₃ of 36 to 84 wt %, B₂O₃ of 5 to 28 wt%, PbO of 0 to 46 wt %, ZnO of 0 to 30 wt %, Al₂O₃ of 0 to 13 wt %, SiO₂of 0 to 10 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0to 3 wt %. The first filler includes at least one selected from thegroup consisting of TiO₂, ZrO₂, ZnO, Al₂O₃, BN, mullite, and MgO.

Each of the first and second glass powders has a softening temperatureof 390 to 550° C. When their softening temperature is smaller than 390°C., the dielectric layer 130 may flow in steps of firing the phosphorouslayers and attaching the front plate and the rear plate of the PDP toeach other after the barrier walls 140 are formed, thereby deterioratingcorrectness in the measurements of the PDP. In contrast, when thesoftening temperature is larger than 550° C., the firing temperature ofthe dielectric layer 130 becomes so high as to change the measurementsof the glass substrate 110, thereby causing it difficult to control themeasurements of the glass substrate 110.

It is preferred that each of the first and second glass powders has anaverage particle diameter of 1 to 10 μm. When each of the first andsecond glass powders has an average particle diameter of less than 1 μm,they have a reduced workability. In contrast, when each of the first andsecond glass powders has an average particle diameter of more than 10μm, the dielectric layer 130 is not sufficiently compacted while beingbaked, so that the dielectric layer 130 may be porous.

Also, each of the first and second glass powders preferably has athermal expansive coefficient of 63×10⁻⁷ to 83×10⁻⁷/° C. When thethermal expansive coefficient is smaller than 63×10⁻⁷/° C., the glasssubstrate 110 may be convexly bent. In contrast, when the thermalexpansive coefficient is larger than 83×10⁻⁷/° C., the glass substrate110 may be concavely bent or the surface of the dielectric layer 130 maycrack. However, even when each of the first and second glass powderspreferably has a thermal expansive coefficient of 95×10⁻⁷/° C., thethermal expansive coefficient can be lowered to 83×10⁻⁷/° C. by mixing aproper amount of the first filler with the first and second glasspowders. Therefore, it will do if each of the first and second glasspowders preferably has a thermal expansive coefficient of 63×10⁻⁷ evenup to 95×10⁻⁷/° C.

It is preferred that each of the first and second glass powders has adielectric constant of 11 to 26. When the dielectric constant of thedielectric layer 130 is smaller than 11, it is difficult to transfer asignal of the electrode 120 to a discharge space defined by the barrierwalls 140. In contrast, when the dielectric constant of the dielectriclayer 130 is larger than 26, the PDP has too slow a response speed whenthe PDP is driven. Meanwhile, when each of the first and second glasspowders has a dielectric constant of at least 6, the dielectric constantof the dielectric layer 130 can be elevated up to 11 by means of thefirst filler. Therefore, it is also preferred that each of the first andsecond glass powders has a dielectric constant of 6 to 26.

The first filler preferably has an average particle diameter of 0.01 to10 μm. Further, it is preferred that a volumetric ratio of the firstfiller with respect to the glass powder in the dielectric layer is 0.05to 0.67. When the volumetric ratio is less than 0.05, the dielectriclayer 130 has a reflectance of at most 50%, thereby preventing the PDPfrom employing a dielectric layer having a reflectance of at least 50%which is necessary in order to enable the PDP to have an improvedbrightness. Further, in the case in which the volumetric ratio is morethan 0.67, when the softening temperature of the glass powder is low,the dielectric constant is high and thus the response seed is slow. Incontrast, when the softening temperature of the glass powder is high,the degree of firing of the dielectric layer 130 deteriorates, so thatit is difficult for the dielectric layer 130 to have a resistance toetching and the dielectric layer 130 has a dielectric constant of atmost 11.

The dielectric layer 130 having the ingredients as described above has adielectric constant of 8 to 20, a reflectance of 50 to 80%, and anetching rate of 0.1 to 1.0 μm/min with respect to inorganic acid. Whenthe etching rate of the dielectric layer 130 is smaller than 0.1 μm/min,the firing temperature of the dielectric layer 130 may rise above 700°C., thereby deforming the glass substrate 110. In contrast, when theetching rate is larger than 1.0 μm/min, the powder has a reducedresistance to etching, so that even the dielectric layer 130 and theelectrodes 120 may be etched when the barrier wall 140 is etched. Whenthe electrode 120 has been damaged by etching, the electric resistanceof the electrode 120 increases.

The first filler can be classified into two kinds of oxides, which haveweak and strong chemical durability with respect to acid-based etchingsolution, respectively. The first kind of oxide having a weak chemicaldurability with respect to acid-based etching solution reacts with glasspowder while it is baked, thereby deteriorating the chemical durabilityof the reacted glass powder. In contrast, the second kind of oxidehaving a strong chemical durability with respect to acid-based etchingsolution reacts with glass powder while it is baked, thereby increasingthe chemical durability of the reacted glass powder.

Further, when the dielectric layer 130 includes too much first filler,quantity of the first filler, which does not react with the oxide,increases, so that firing strength deteriorates. Therefore, it ispreferred that a ratio of volume of the first filler with respect tovolume of the glass powder in the dielectric layer 130 is not largerthan 0.67. The less the quantity of the first filler is, the more thewhite degree of the dielectric layer 130 deteriorates. However, sincesome PDPs may have a dielectric layer 130 with an unlimited whitedegree, it is unnecessary to define a lower limit of the ratio of volumeof the first filler with respect to volume of the glass powder in thedielectric layer 130.

The dielectric layer 130 may have defect due to either repetition ofprinting and drying processes or screen plate making. The defect due toscreen plate making include irregular thickness of meshes, non-uniformsurface state of meshes, stains of meshes, etc., which may cause defectsuch as pinholes or height difference on the dielectric layer 130.Further, the material of the dielectric layer 130 may be insufficientlyfilled under end portions of the electrodes 120 due to a curl phenomenonin which the end portions of the electrodes 120 formed throughphotolithography and firing are curled up while they are being baked.Then, bubbles may be generated between the electrodes 120 and thedielectric layer 130 to lower the resistance to voltage, thereby causinginsulation breaking, while a PDP operates. Therefore, in forming thedielectric layer 130, either a printing method or a green tapeattachment method, which will be described later, must be employedaccording to material or characteristics of its shape.

The barrier walls 140 are formed on the upper surface of the dielectriclayer 130. Specifically, a slurry is formed in a shape of green tapeshaving a predetermined thickness and is then attached to the uppersurface of the dielectric layer 130. Then, the attached green tapes aresubjected to photolithography and etching, thereby the barrier walls 140having a shape of patterns.

The barrier wall 140 is made in a shape of green tapes by adding organicmaterial and additive to mixture of a second filler and at least oneglass powder selected from the group consisting of the third, fourth,and fifth glass powders.

The third glass powder comprises ZnO of 0 to 48 wt %, SiO₂ of 0 to 21 wt%, B₂O₃ of 25 to 56 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to38 wt %, and BaO+CaO+MgO+SrO of 0 to 15 wt %. The fourth glass powdercomprises PbO of 25 to 65 wt %, ZnO of 0 to 35 wt %, SiO₂ of 0 to 26 wt%, B₂O₃ of 0 to 30 wt %, Al₂O₃+SnO₂ of 0 to 13 wt %, Na₂O+K₂O+Li₂O of 0to 19 wt %, BaO of 0 to 26 wt %, and CaO+MgO+SrO of 0 to 13 wt %. Thefifth glass powder comprises PbO of 35 to 55 wt %, B₂O₃ of 18 to 25 wt%, ZnO of 0 to 35 wt %, BaO of 0 to 16 wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9wt %, CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %,and CaO+MgO+SrO of 0 to 13 wt %. The second filler includes at least oneselected from the group consisting of TiO₂, ZrO₂, ZnO, Al₂O₃, BN,mullite, and MgO.

Herein, the third glass powder has a softening temperature of 460 to630° C., and each of the fourth and fifth glass powders has a softeningtemperature of 390 to 550° C. In the case where the softeningtemperature is smaller than 460° C. and 390° C., respectively, when thephosphorous layers 150 are baked after the barrier walls 140 are formedor after the front and rear plates are attached to each other, thebarrier walls 140 may be deformed so that the barrier walls 140 may havemuch irregular heights and their upper portions may have much irregularwidths. In contrast, in a case where the softening temperature is largerthan 630° C. and 550° C., respectively, the firing temperature of thebarrier wall 140 increases, thereby causing it difficult to control themeasurements of the glass substrate 110.

The third glass powder has a thermal expansive coefficient of 64×10⁻⁷ to105×10⁻⁷/° C., and each of the fourth and fifth glass powders preferablyhas a thermal expansive coefficient of 63×10⁻⁷ to 110×10⁻⁷/° C. When thethermal expansive coefficient is smaller than 63×10⁻⁷/° C. and 63×10⁻⁷/°C., respectively, the glass substrate 110 may be convexly bent. Incontrast, when the thermal expansive coefficient is larger than105×10⁻⁷/° C. or 110×10⁻⁷/° C., respectively, the glass substrate 110may be concavely bent or the surface of the glass substrate 110 maycrack. However, since the thermal expansive coefficient can be changedby adjusting the amount of the filler in the barrier wall 140, each ofthe third, fourth, and fifth glass powders may preferably have a thermalexpansive coefficient of 63×10⁻⁷ even up to 110×10⁻⁷/° C.

Each of the third, fourth, and fifth glass powders has an averageparticle diameter of 0.5 to 17 μm. When the glass powder has an averageparticle diameter of smaller than 0.5 μm, it is difficult to make pastefor the barrier wall from the glass powder. In contrast, when theconductive metal powder has an average particle diameter of larger than17 μm, it is difficult to enable the barrier walls to be sufficientlycompact through firing after forming the barrier walls.

Each of the third, fourth, and fifth glass powders has a dielectricconstant of 5 to 20. In the case where the dielectric constant issmaller than 5, a drive voltage characteristic is deteriorated when amanufactured PDP is driven. In contrast, in the case where thedielectric constant is larger than 20, crosstalk and erroneous dischargemay occur when the manufactured PDP is driven.

Further, the second filler has an average particle diameter of at most10 μm. Also, a volumetric ratio of the first filler with respect to theglass powder for the barrier walls is 0.05 to 0.67, which will bedescribed later.

Organic material and additive are added to the material for the barrierwalls as described above, so as to form a slurry with a viscosity of 500to 40000 cP (centi-poise) in a shape of green tapes, thereby formingpreliminary barrier walls. Then, the preliminary barrier walls in ashape of green tapes are attached to the upper surface of the dielectriclayer 130 through lamination, and are then simultaneously baked togetherwith the dielectric layer 130 at a temperature above 400° C. Herein, itis preferred that the preliminary barrier walls in a shape of greentapes have a thickness of 100 o 180 μm.

In order to simultaneously bake the dielectric layer 130 and the barrierwalls, a difference between the thermal expansive coefficients of themmust have a value of at most 10%, and a difference between the softeningtemperatures of them must have a value of at most 20° C. If thedifference between the thermal expansive coefficients of them has avalue larger than 10%, the dielectric layer 130 and the barrier wallsmay be separated from each other, thereby allowing bubbles to be formedbetween them, when they have been simultaneously baked. Further, theglass substrate 110 may be bent due to the difference between thethermal expansive coefficients of them, thereby preventing the rearplate from being attached to the front plate.

Further, when the difference between the softening temperatures of themhas a value larger than 20° C., end portions of the dielectric layer 130and the barrier walls may be curled up or may come off, thereby allowingbubbles to be formed between them. When too many bubbles exist in aninterface between the dielectric layer 130 and the barrier walls, eachof the dielectric layer 130 and the barrier walls may have a sparseinternal structure, thereby having large fragility and deterioratedstrength. Further, when too many bubbles exist in an interface betweenthe dielectric layer 130 and the barrier walls, the bubbles may comeinto the dielectric layer 130 and the barrier walls while the dielectriclayer 130 and the barrier walls are baked, so that the dielectric layer130 and the barrier walls may have deteriorated properties andinsulation breaking may occur while a PDP operates.

In order to prepare the material for the barrier walls in a form ofslurry, organic materials and additives are necessary. The organicmaterials include a binding agent which provides strength to the barrierwalls, a solvent which dissolves the material of the barrier walls andprovides fluidity necessary in milling and casting to the barrier walls,and a plasticizer which improves workability of the barrier walls. Theadditives include a defoaming agent for reducing generation of bubbles,a dispersing agent for aiding dispersion of inorganic material, dyes,and lubricating oil.

The binding agent includes at least one selected from the groupconsisting of Polyvinyl butyral, Polyvinyl alcohol, Polyvinyl acetate,Poly Methyl Metaacrylate, Poly ethyl acrylate, Poly acrylic acid, EthylCellulose, Hydroxyethyl cellulose, Methyl cellulose, Carboxymethylcellulose, Acrylic ester, and Ammonium Polyacrylate. The solventincludes at least one selected from the group consisting of Ethylalcohol, n-Butyl alcohol, Toluene, Water, Methyl alcohol, n-Propylalcohol, Isopropyl alcohol, Ethylene Glycol, Benzaldehide, Ethylacetate,Cyclohexane, Isopropyl acetate, n-Octyl alcohol, Benzyl alcohol,Glycerol, Acetone, Methyl Ethyl Keton, Propionic acid, n-Octanoic acid,n-Hexane, O-Xylene, MIBK, Xylene, and Butanyl. The plasticizer includesat least one selected from the group consisting of Water, EthyleneGlycol, Diethylene Glycol, Tetraethylene glycol, Glycerine, Dimethylphtalate, Dibutyl phtalate, Benzyl butyl phthalate, poly propyleneglycol, Phosphate, Phthalate, Glycol ether, and Polyethylen glycol.

As the additives, typical additives are used.

The binding agent must experience a complete thermal decompositionthrough the drying and firing process. If the binding agent is notthermally decomposed, carbon residue may exist in the barrier walls,thereby greatly decreasing an insulation strength of the barrier walls.The solvent is selected in consideration of viscosity of slurry anddrying speed according to the thickness of the green tapes and casting,solubility and speed of dissolution of adhesive agent and other organicmaterials, etc. The plasticizer must be selected in consideration ofcompatibility of the plasticizer with the binding agent. If aplasticizer shows an incompatibility with respect to the binding agentaccording to temperature increase, the plasticizer escapes out of thegreen tapes during the drying process, so that the green tapes havefragility. The organic material is selected in consideration ofproperties such as viscosity in milling, viscosity in casting, thicknessof the green tapes, strength of the green tapes, percentage ofelongation, and workability. When the quantity of the organic materialis too much, defoamation process must be performed for long time. Incontrast, when the quantity of the organic material is too little, anefficiency of milling for preparing the slurry deteriorates.

As shown in FIG. 2, each barrier wall 245 may include a plurality ofwall layers 245 ⁻¹, 245 ⁻², . . . 245 _(−(n−1)), 245 _(−n) which areprepared from different materials having different etching rates toinorganic acid. Herein, if the multiple wall layers 245 ⁻¹, 245 ⁻², . .. , 245 _(−(n−1)), 245 _(−n) constituting the barrier wall 245 are namedfirst, second, . . . , (n−1)^(th), and n^(th) wall layers, respectively,the (n−1)^(th) wall layer has an etching rate with respect to inorganicacid, which is larger than or equal to that of the n^(th) wall layer. Asa result, when the barrier wall 245 is formed through etching, sidesurfaces of the barrier wall 245 can be formed nearly vertically,thereby forming a rectangular discharge space.

Further, each of the wall layers 245 ⁻¹, 245 ⁻², . . . , 245 _(−(n−1)),245 _(−n) must have a thickness corresponding to 5% to 95% of the entirethickness of the barrier wall 245. If any of the wall layers has athickness, which is either smaller than 5% or larger than 95% of theentire thickness of the barrier wall 245, the thickness of that walllayer is too small or too large to have an effect by the adjustment ofetching rate as described above, thereby making it useless to form thebarrier wall 245 from at least two kinds of different materials.

When barrier walls are formed in a shape of green tapes from mixture inwhich organic material and additives are added to the material of thebarrier walls, which has the composition and properties described aboveaccording to the first embodiment of the present invention, the barrierwalls have a dielectric constant of 5 to 18, a reflectance of 40 to 80%,and an etching rate of 1.0 to 50.0 μm/min.

Further, the phosphorous layers 150 include red, green, and bluephosphorous layers formed on side and bottom surfaces of the barrierwalls 140, each of the phosphorous layers having a thickness of at least10 μm.

Second Embodiment

FIG. 2 is a sectional view of a rear plate of a plasma display panelaccording to the second embodiment of the present invention.

As shown, a dielectric layer 230 and barrier walls 245 each are arrangedin a shape of green tapes, the dielectric layer 230 is formed on uppersurfaces of an electrode 220 and a glass substrate 210, and then thebarrier walls 245 are formed on an upper surface of the dielectric layer230, so that a rear plate 200 according to the second embodiment of thepresent invention is completed.

The electrode 220 according to the second embodiment is the same as theelectrode according to the first embodiment, and the dielectric layer230 according to the second embodiment is made from the same material asthat of the dielectric layer 130 according to the first embodiment.However, in forming the dielectric layer 230 according to the secondembodiment, organic material and additives are added to material of thedielectric layer 130 according to the first embodiment, which is thenformed in a shape of green tapes and attached to the upper surfaces ofthe electrode 220 and the glass substrate 210. Further, the barrierwalls 245 according to the second embodiment is formed on the uppersurface of the dielectric layer 230 in the same manner as that accordingto the first embodiment, and the dielectric layer 230 and the barrierwalls 245 are simultaneously baked at a temperature above 400° C. asthose according to the first embodiment.

The other constructions according to the second embodiment are the sameas those according to the first embodiment.

Third Embodiment

FIG. 3 is a sectional view of a rear plate of a plasma display panelaccording to the third embodiment of the present invention.

As shown, composition and characteristics of each functional layer of arear plate according to the third embodiment of the present invention isthe same as the composition and characteristics of each functional layerof the rear plate according to the second embodiment of the presentinvention. In description of only the differences between them, adielectric layer 330 and barrier walls 345 are prepared in a shape ofgreen tapes having a thickness of 10 to 30 μm and 100 to 180 μm,respectively, and are integrated with each other. Thereafter, thedielectric layer 330 is attached to upper surfaces of electrodes 320 anda glass substrate 310. Then, they are baked at a temperature above 400°C., so that the dielectric layer 330 and the barrier walls 345 arecompleted.

The other constructions according to the third embodiment are the sameas those according to the second embodiment.

The etching rate described in the first, second, and third embodimentsis defined by an equation, etching rate={(M1−M2)/6.25}×100. In thisequation, M1 implies mass of a substrate having a size of 2.5 cm×2.5 cm,on the entire surface of which material for the dielectric layer or thebarrier walls has been applied and then baked. M2 implies mass of thesubstrate, measured after the substrate is wet-etched for two minutes,is washed for one minute by ultrasonic wave and then for one minute byflowing water, and is then dried.

Next, measured properties of each functional layer of the rear platemanufactured as described above will be described.

Experiment 1

EPH-200TR5611 photosensitive electrode paste having a specificresistance of 2.7×10⁻⁶ Ωcm, made by Taiyo Ink company of Japan, wasapplied with a thickness of 4˜6 μm on an upper surface of a glasssubstrate by means of a polyester screen Mask of #200 mesh and was thendried for fifteen minutes at 90° C., thereby forming an electrode layer.Thereafter, the electrode layer formed on the glass substrate wasexposed to light and was then developed, so that electrodes having ashape of patterns were formed. In the exposure step, the electrode layerwas exposed to light of 500 mJ emitted by a mirror reflected parallelbeam illuminator (MRPBI) equipped with a mercury lamp. Also, in thedevelopment step, solution containing sodium carbonate of 0.4 wt % at atemperature of 30° C. was sprayed for thirty seconds at a pressure of0.2 Mpa, and then pure water at 25° C. was sprayed for thirty seconds ata pressure of 0.1 Mpa onto the electrode substrate. Then, the electrodesdried after being developed were baked for fifteen minutes at a maximumtemperature of 550° C.

A dielectric layer with a thickness of 22 μm was formed on uppersurfaces of the electrodes through screen printing using a SUS screenMask of #200 mesh, and was then dried for ten minutes at 120° C. Table 1shows composition of the dielectric layer. TABLE 1 Composition of thedielectric layer according to experiment 1: Gradients of glass powder(wt %) 1^(st) Class PbO SiO₂ B2O3 Al₂O₃ ZnO NaO BaO filler Dielectric43.5 16 8 2.5 29 1 TiO₂ + layer ZnO₂ + Al₂O₃

Glass powder of the dielectric layer having the composition shown intable 1 has a softening temperature of 460° C. When the dielectric layerhas been baked for fifteen minutes at a maximum temperature of 530° C.,the dielectric layer has a dielectric constant of 12.5, a reflectance of70%, an etching rate of 0.5 μm/min with respect to inorganic acid.

The barrier walls were formed in a shape of green tapes with threelayers and were then laminated on the upper surface of the dielectriclayer. Table 2 shows composition of each layer of the barrier walls.TABLE 2 Composition of each layer of the barrier walls according toexperiment 1: Gradients of glass powder (wt %) Li₂O + Class PbO ZnO SiO₂B₂O₃ Al₂O₃ + ZnO₂ Na₂O + K₂O BaO CaO + MgO + SrO Filler Partition 1^(st)40 22 6 18 2 12 0 1 TiO₂ + ZnO₂ + Al₂O₃ wall layer 2^(nd) 41 30 5 18 2 20 2 ZrO₂ + Al₂O₃ layer 3^(rd) 55 20 0 16 1 5 1 2 TiO₂ + ZrO₂ + Al₂O₃layer

In forming the barrier walls in a shape of green tapes, B-44 and B-48,which are binders having different molecular weights from amongPolyMethyl Meta Acrylate-series (PMMA-series) binders manufactured byRohm and Hass company, were employed, mixture of ethyl alcohol andtoluene by 1:1 was employed as solvent, and dimethyl phtalate wasemployed as a plasticizer. Further, menhaden fish oil was employed as adispersing agent, and stearic acid was employed as a lubricating agent.Herein, a binder of 6 wt %, a solvent of 30 wt %, a plasticizer of 8 wt%, a dispersing agnet of 1 wt %, and a lubricating agent of 0.3 wt %were added in the powder mixture of 100 wt % for the barrier walls, inwhich glass powder and filler are mixed.

After the additives described were added, the barrier walls were formedin a shape of green tapes with three layers by means of a tape caster.Then, each barrier wall was solidified to have a total thickness of 196μm, in which a thickness ratio of (the first layer):(the secondlayer):(the third layer) is 1:(0.9):(0.8). Thereafter, the barrier wallshaving a shape of green tapes were attached to the upper surface of thedielectric layer through laminating by a roller at a temperature of 105°C. and a pressure of 0.3 Mpa, and were then baked together with thedielectric layer at a maximum temperature of 530° C. for 15 minutes.Then, each of the formed barrier walls were formed to have a thicknessof 150 μm.

Table 3 shows properties of the barrier walls formed as described above.TABLE 3 Measured properties of each layer of the barrier wall accordingto experiment 1: Thermal Average Softening expansive particle Etchingtemperature coefficient diameter Dielectric Reflection rate Class (° C.)(×10⁻⁷/° C.) (μm) constant ratio(%) (μm/Min) Partition 1^(st) 40 22 6 182 12 wall layer 2^(nd) 41 30 5 18 2 2 layer 3^(rd) 55 20 0 16 1 5 layer

Photosensitive material was applied on the upper surfaces of the barrierwalls, was exposed to light by means of a photo mask, and was thendeveloped. Thereafter, inorganic acid was sprayed onto the developedphotosensitive material at a pressure of 2 kgf/cm², so that the barrierwalls were completely formed in a shape of patterns through a selectivewet etching. Then, each barrier wall had an uppermost portion having awidth of 50 μm and a lowermost portion having a width of 120 μm.

Thereafter, red, green, and blue phosphors were printed with a thicknessof 17 μm on side and bottom surfaces of the barrier walls, therebyforming phosphorous layers covered on the barrier walls.

Table 4 shows properties of PDPs employing a rear plate according toexperiment 1 and a conventional rear plate, respectively. TABLE 4Measured properties of PDPs employing a rear plate according toexperiment 1 and a conventional rear plate: PDP PDP employing employingrear plate conventional of Class rear plate experiment 1 Pitch 250 μm250 μm Number of firings of rear plate 4 times 3 times Discharge space100% 106% Optical White Peak brightness 100% 132% properties Colortemperature(K) 8500 8802 Contrast 100% 128% Electrical Voltage margin100% 145% properties Power consumption 100%  89% Module efficiency 100%125% reliability High temp./low temp. erroneous No No dischargevibration/drop test No No progressive progressive defect defect Othernoise (dB) 100%  75% properties

As apparent from table 4, a PDP employing a rear plate according toexperiment 1 of the present invention has shown improvement incomparison with a PDP employing a conventional rear plate, whichincludes 6% increase of discharge space, 32% increase of whitebrightness, 302 k increase of color temperature, 28% increase ofcontrast, 45% of voltage margin, 11% decrease of power consumption, 25%increase of PDP efficiency, and 25% decrease of noise. In table 4,“Pitch” implies a distance between centers of adjacent two barrierwalls.

Experiment 2

Electrodes in experiment 2 are the same as the electrodes in experiment1, excepting that the firing temperature in experiment 2 is 570° C.

An electrode layer formed on a glass substrate was exposed to light anddeveloped, so that electrodes having a shape of patterns were formed. Inthe exposure step, the electrode layer was exposed to light of 500 mJemitted by a mirror reflected parallel beam illuminator equipped with amercury lamp. Also, in the development step, solution containing sodiumcarbonate of 1.0 wt % at a temperature of 30° C. was sprayed for thirtyseconds at a pressure of 0.2 Mpa, and then pure water at 30° C. wassprayed for thirty seconds at a pressure of 0.1 Mpa onto the electrodesubstrate. Then, the electrodes dried after being developed were bakedfor fifteen minutes at a maximum temperature of 570° C.

Thereafter, the dielectric layer was formed in a form of a green tapeand was then laminated on the upper surfaces of the electrodes. Table 5shows composition of the dielectric layer. TABLE 5 Composition of thedielectric layer in experiment 2 Glass powder (wt %) Class PbO SiO₂ B₂O₃Al₂O₃ ZnO NaO BaO Filler Dielectric 60 15 19 6 TiO₂ + layer ZnO₂ + Al₂O₃

Glass powder of the dielectric layer having the composition shown intable 5 has a softening temperature of 450° C. In order to prepare thedielectric layer in a shape of a green tape, poly vinyl buryral and B98manufactured by Monsanto co., Ltd. were employed as a binder, mixtureincluding MEK, ethyl alcohol, and n-butyl alcohol at a weight ratio of3:1:1 was employed as a solvent, dibutyl phthalate was employed as aplasticizer, and SN-9228, manufactured by Sanocof co., Ltd., wasemployed as a dispersing agent. Herein, a binder of 6 wt %, a solvent of30 wt %, a plasticizer of 1 wt %, and a dispersing agnet of 8 wt % wereadded in the powder mixture of 100 wt % for the dielectric layer, inwhich glass powder and filler are mixed.

In forming the dielectric layer, slurry including the above-mentionedadditives and having a viscosity of 8000±500 cps was prepared in a formof a green tape with a thickness of 37 μm, and was then attached toupper surfaces of the electrodes and the glass substrate throughlaminating by a roller at a temperature of 95° C. and a pressure of 0.25Mpa.

Thereafter, the attached green tape was baked at a maximum temperatureof 530° C. for 15 minutes. Then, the completed dielectric layer had adielectric constant of 18.0, a reflectance of 73%, an etching rate of0.3 μm/min with respect to inorganic acid.

Thereafter, barrier walls equal to those according to experiment 1 wereattached to the upper surface of the dielectric layer through laminatingby a roller at a temperature of 105° C. and a pressure of 0.3 Mpa, andwere then baked together with the dielectric layer at a maximumtemperature of 530° C. for 15 minutes. In this case, the dielectriclayer was formed to have a thickness of 25 μm, and each of the formedbarrier walls were formed to have a thickness of 150 μm, in which thefirst, second, and third layers of each barrier wall have 56 μm, 50 μm,44 μm, respectively. Also, the widths of the uppermost and lowermostportions of each barrier wall, and the pitch between barrier walls werearranged to be the same as those in experiment 1.

Thereafter, phosphorous layers were formed in the same manner as that inexperiment 1, excepting that each phosphorous layer was formed to have athickness of 14 μm.

Table 6 shows properties of PDPs employing a rear plate according toexperiment 2 and a conventional rear plate, respectively. TABLE 6Measured properties of PDPs employing a rear plate according toexperiment 2 and a conventional rear plate: PDP PDP employing employingrear plate conventional of Class rear plate experiment 2 Pitch 250 μm250 μm Number of firings of rear plate 4 times 3 times Discharge space100% 106% Optical White Peak brightness 100% 130% properties Colortemperature(K) 8500 8796 Contrast 100% 125% Electrical Voltage margin100% 137% properties Power consumption 100%  89% Module efficiency 100%121% reliability High temp./low temp. erroneous No No dischargevibration/drop test No No progressive progressive defect defect Othernoise (dB) 100%  75% properties

As apparent from table 6, like the PDP employing a rear plate accordingto experiment 1 of the present invention, a PDP employing a rear plateaccording to experiment 2 of the present invention has shown improvementin electric and optical characteristics and reliability, in comparisonwith a PDP employing a conventional rear plate.

Experiment 3

Electrodes in experiment 3 are the same as the electrodes in experiment2.

An electrode layer and a barrier wall layer were prepared in a shape ofa green tape, respectively, and were then integrated with each other,thereby forming a lamination of electrode layer/barrier wall layerhaving a form of a green tape.

Thereafter, the lamination of electrode layer/barrier wall layer waslaminated on the upper surfaces of the electrodes. Tables 7 and 8 showcomposition of the dielectric layer and the barrier wall layer,respectively. TABLE 7 Composition of the dielectric layer in experiment3: Gradients of glass powder (wt %) Class PbO SiO₂ B₂O₃ Al₂O₃ ZnO NaOBaO Filler Dielectric 53 13 6 12 10 0 2 TiO₂ + layer Al₂O₃

Glass powder of the dielectric layer having the composition shown intable 7 has a softening temperature of 535° C. In order to prepare thedielectric layer in a shape of a green tape, PVB and B98 manufactured byMonsanto co., Ltd. were employed as a binder, mixture including toluene,ethanol, and n-butyl alcohol was employed as a solvent, dibutylphthalate was employed as a plasticizer, and SN-9228, manufactured bySanoncof co., Ltd., was employed as a dispersing agent. Herein, a binderof 12 wt %, a solvent of 20 wt %, a plasticizer of 1 wt %, and adispersing agent of 4 wt % were added in the powder mixture of 100 wt %for the dielectric layer, in which glass powder and filler are mixed.The solvent of 20 wt % includes toluene of 4 wt %, ethanol of 1 wt %,and n-butyl alcohol of 1 wt %, mixed therein. As a result, a dielectriclayer was formed in a shape of a green tape having a viscosity of8000±500 cps.

Next, the dielectric layer formed as described above was baked at amaximum temperature of 550° C. for 15 minutes. Then, the completeddielectric layer was observed to have a dielectric constant of 13.2, areflectance of 69%, an etching rate of 0.12 μm/min with respect toinorganic acid. TABLE 8 Composition of the barrier wall in experiment 3:Gradients of glass powder (wt %) Class PbO ZnO SiO₂ B₂O₃ Al₂O₃ + ZnO₂Li₂O + Na₂O + K₂O BaO CaO + Mg + SrO Filler 1^(st) 0 19 6 37 0 38 0 0TiO₂ + ZnO₂ + Al₂O₃ layer 2^(nd) 0 22 21 30 5 21 1 0 ZrO₂ + Al₂O₃ layer

In order to prepare the dielectric layer having a composition as shownin Table 8 in a shape of a green tape, PVB manufactured by Monsanto co.,Ltd. was employed as a binder, mixture including toluene and isopropylalcohol was employed as a solvent, dibutyl phthalate manufactured byYakuri company was employed as a plasticizer, and KD-1 manufactured byICI Chemical was employed as a dispersing agent.

Herein, a binder of 10 wt %, a solvent of 20 wt %, a plasticizer of 20wt %, and a dispersing agent of 1 wt % were added in the powder mixtureof 100 wt % for the barrier walls, in which glass powder and filler aremixed. The solvent of 20 wt % includes toluene of 8 wt % and isopropylalcohol of 2 wt %, mixed therein. As a result, the barrier walls wereformed in a shape of green tapes having a viscosity of 9500±500 cps. Inthis case, each of the barrier walls consists of two overlapping layers.

Table 9 shows properties of the barrier wall according to experiment 3.TABLE 9 Properties of the barrier wall according to experiment 3:Thermal Average Softening expansive particle Reflection Etchingtemperature coeffic. dia. Dielectric ratio rate class (° C.) (×10⁻⁷/°C.) (μm) const. (%) (μm/Min) Partition 1^(st) 475 79 3.5 20 65 42.0 walllayer 2^(nd) 481 93 9.1 17 67 30.9 layer

Hereinafter, a method of integrating the dielectric layer and thebarrier wall layer with each other will be briefly described.

After the dielectric layer was cast, the first and second layers of thebarrier wall layer were sequentially cast on the upper surface of thedielectric layer, and then each layer was preliminary dried at 75° C.,so that a lamination of dielectric layer/barrier wall layer having ashape of an integrated green tape was formed. Then, the lamination ofdielectric layer/barrier wall layer was completely dried at 145° C., andwas then attached to the upper surfaces of the electrodes and the glasssubstrate by a roller at a pressure of 0.3 MPa and temperature of 105°C. Thereafter, the lamination of dielectric layer/barrier wall layer wasbaked for fifteen minutes at a maximum temperature of 550° C., so thatthe dielectric layer was formed to have a thickness of 23 μm and thebarrier wall layer was formed to have a thickness of 130 μm. In thebarrier wall layer, the first layer was formed to have a thickness of103 μm and the second layer was formed to have a thickness of 27 μm.

Thereafter, barrier walls were formed by working the partition layer inthe same manner as in experiment 1, so that each barrier wall had anuppermost portion with a width of 60 μm and a lowermost portion with awidth of 130 μm.

Further, phosphorous layers were formed in the same manner as inexperiment 1. Each phosphorous layer was formed to have a thickness of13 μm.

Table 10 shows properties of PDPs employing a rear plate according toexperiment 3 and a conventional rear plate, respectively. TABLE 10Measured properties of PDPs employing a rear plate according toexperiment 3 and a conventional rear plate: PDP PDP employing employingrear plate conventional of Class rear plate experiment 3 Pitch 220 μm220 μm Number of firings of rear plate 4 times 3 times Discharge space100% 105% Optical White Peak brightness 100% 125% properties Colortemperature(K) 8500 8647 Contrast 100% 120% Electrical Voltage margin100% 125% properties Power consumption 100%  92% Module efficiency 100%115% reliability High temp./low temp. erroneous No No dischargevibration/drop test No No progressive progressive defect defect Othernoise (dB) 100%  75% properties

As apparent from table 10, like the PDPs employing rear plates accordingto experiments 1 and 2, a PDP employing a rear plate according toexperiment 3 of the present invention has shown improvement in electricand optical characteristics and reliability, in comparison with a PDPemploying a conventional rear plate.

Further, as noted from experiments 1, 2, and 3 of the present invention,in a PDP employing a rear plate according to the present invention, eachbarrier wall has a narrower lower portion than that in a PDP employingthe conventional rear plate, so that the discharge space increases 5%and the number of firing times can be reduced.

INDUSTRIAL APPLICABILITY

As can be seen from the foregoing, in a rear plate of a plasma displaypanel according to the present invention, a dielectric layer or abarrier wall layer is formed by forming slurry in a tape of a green tapeand then attaching the green tape to upper surfaces of electrodes and aglass substrate. Therefore, a PDP employing a rear plate according tothe present invention has superior electric and optical characteristics.

While this invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not limited to thedisclosed embodiment and the drawings, but, on the contrary, it isintended to cover various modifications and variations within the spiritand scope of the appended claims.

1. A rear plate of a plasma display panel, the rear plate comprising: aglass substrate; electrodes formed in a shape of patterns on an uppersurface of the glass substrate; a dielectric layer formed on uppersurfaces of the electrode and the upper surface of the glass substrate;barrier walls formed in a shape of a pattern through etching on an uppersurface of the dielectric layer; and phosphorous layers formed on sidesurfaces and bottom surfaces of the barrier walls, wherein: theelectrodes has a thickness of 2 to 8 μm and a specific resistance of1.0×10⁻⁶ to 5.0×10⁻⁶ Ωcm; the dielectric layer is made from a firstmixture which includes a first filler and at least one glass powderselected from among a first glass powder and a second glass powder, thefirst glass powder including PbO of 30 to 80 wt %, ZnO of 0 to 20 wt %,SiO₂ of 0 to 20 wt %, B₂O₃ of 5 to 40 wt %, Al₂O₃ of 0 to 12 wt %,Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0 to 5 wt %, thesecond glass powder including Bi₂O₃ of 36 to 84 wt %, B₂O₃ of 5 to 28 wt%, PbO of 0 to 46 wt %, ZnO of 0 to 30 wt %, Al₂O₃ of 0 to 13 wt %, SiO₂of 0 to 10 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0to 3 wt %, each of the first and second glass powders having an averageparticle diameter of 1 to 10 μm, a softening temperature of 390 to 550°C., and a thermal expansive coefficient of 63×10⁻⁷ to 83×10⁻⁷/° C., thefirst filler having an average particle diameter of 0.01 to 10 μm, thedielectric layer having a dielectric constant of 8 to 20, a reflectanceof 50 to 80%, an etching rate of 0.01 to 1.0 μm/min with respect toinorganic acid, and a thickness of 10 to 30 μm; the barrier walls aremade from a second mixture which includes a second filler, organicmaterial, additives, and at least one glass powder selected from thegroup consisting of a third, fourth, and fifth glass powders, the thirdglass powder including ZnO of 0 to 48 wt %, SiO₂ of 0 to 21 wt %, B₂O₃of 25 to 56 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 38 wt %,and BaO+CaO+MgO+SrO of 0 to 15 wt %, the fourth glass powder includingPbO of 25 to 65 wt %, ZnO of 0 to 35 wt %, SiO₂ of 0 to 26 wt %, B₂O₃ of0 to 30 wt %, Al₂O₃+SnO₂ of 0 to 13 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %,BaO of 0 to 26 wt %, and CaO+MgO+SrO of 0 to 13 wt %, the fifth glasspowder including PbO of 35 to 55 wt %, B₂O₃ of 18 to 25 wt %, ZnO of 0to 35 wt %, BaO of 0 to 16 wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9 wt %,CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %, andCaO+MgO+SrO of 0 to 13 wt %, the third glass powder having a softeningtemperature of 460 to 630° C., a thermal expansive coefficient of64×10⁻⁷ to 105×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, each of the fourth and fifth glass powders having a softeningtemperature of 390 to 550° C., a thermal expansive coefficient of63×10⁻⁷ to 110×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, the second filler having an average particle diameter of 0.01 to 10μm, the barrier walls being formed with a height of 100 to 180 μm byattaching a barrier wall layer formed in a shape of green tapes to anupper surface of the dielectric layer, firing the barrier wall layertogether with the dielectric layer at a temperature between 400° C. and700° C., and then etching the barrier wall layer, the barrier wall layerhaving a dielectric constant of 5 to 18, a reflectance of 40 to 80%, anetching rate of 1.0 to 50.0 μm/min with respect to inorganic acid; thephosphorous layers have a thickness of 10 to 50 μm; and a differencebetween the thermal expansive coefficients of the dielectric layer andthe barrier wall layer has a percentage between 0 and 10%, and adifference between the softening temperatures of the dielectric layerand the barrier wall layer has a value between 0 and 20° C.
 2. A rearplate of a plasma display panel, the rear plate comprising: a glasssubstrate; electrodes formed in a shape of patterns on an upper surfaceof the glass substrate; a dielectric layer formed on upper surfaces ofthe electrode and the upper surface of the glass substrate; barrierwalls formed in a shape of a pattern through etching on an upper surfaceof the dielectric layer; and phosphorous layers formed on side surfacesand bottom surfaces of the barrier walls, wherein: the electrodes has athickness of 2 to 8 μm and a specific resistance of 1.0×10⁻⁶ to 5.0×10⁻⁶Ωcm; the dielectric layer is made from a first mixture which includes afirst filler, organic material, additives, and at least one glass powderselected from among a first glass powder and a second glass powder, thefirst glass powder including PbO of 30 to 80 wt %, ZnO of 0 to 20 wt %,SiO₂ of 0 to 20 wt %, B₂O₃ of 5 to 40 wt %, Al₂O₃ of 0 to 12 wt %,Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0 to 5 wt %, thesecond glass powder including Bi₂O₃ of 36 to 84 wt %, B₂O₃ of 5 to 28 wt%, PbO of 0 to 46 wt %, ZnO of 0 to 30 wt %, Al₂O₃ of 0 to 13 wt %, SiO₂of 0 to 10 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0to 3 wt %, each of the first and second glass powders having an averageparticle diameter of 1 to 10 μm, a softening temperature of 390 to 550°C., and a thermal expansive coefficient of 63×10⁻⁷ to 83×10⁻⁷/° C., thefirst filler having an average particle diameter of 0.01 to 10 μm, thedielectric layer having a dielectric constant of 8 to 20, a reflectanceof 50 to 80%, an etching rate of 0.01 to 1.0 μm/min with respect toinorganic acid, and a thickness of 10 to 30 μm, the dielectric layerbeing formed in a shape of a green tape and then attached to uppersurfaces of the electrodes; the barrier walls are made from a secondmixture which includes a second filler, organic material, additives, andat least one glass powder selected from the group consisting of a third,fourth, and fifth glass powders, the third glass powder including ZnO of0 to 48 wt %, SiO₂ of 0 to 21 wt %, B₂O₃ of 25 to 56 wt %, Al₂O₃ of 0 to12 wt %, Na₂O+K₂O+Li₂O of 0 to 38 wt %, and BaO+CaO+MgO+SrO of 0 to 15wt %, the fourth glass powder including PbO of 25 to 65 wt %, ZnO of 0to 35 wt %, SiO₂ of 0 to 26 wt %, B₂O₃ of 0 to 30 wt %, Al₂O₃+SnO₂ of 0to 13 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %, BaO of 0 to 26 wt %, andCaO+MgO+SrO of 0 to 13 wt %, the fifth glass powder including PbO of 35to 55 wt %, B₂O₃ of 18 to 25 wt %, ZnO of 0 to 35 wt %, BaO of 0 to 16wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9 wt %, CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt%, Na₂O+K₂O+Li₂O of 0 to 19 wt %, and CaO+MgO+SrO of 0 to 13 wt %, thethird glass powder having a softening temperature of 460 to 630° C., athermal expansive coefficient of 64×10⁻⁷ to 105×10⁻⁷/° C., and anaverage particle diameter of 0.5 to 17 μm, each of the fourth and fifthglass powders having a softening temperature of 390 to 550° C., athermal expansive coefficient of 63×10⁻⁷ to 110×10⁻⁷/° C., and anaverage particle diameter of 0.5 to 17 μm, the second filler having anaverage particle diameter of 0.01 to 10 μm, the barrier walls beingformed with a height of 100 to 180 μm by attaching a barrier wall layerformed in a shape of green tapes to an upper surface of the dielectriclayer, firing the barrier wall layer together with the dielectric layerat a temperature between 400° C. and 700° C., and then etching thebarrier wall layer, the barrier wall layer having a dielectric constantof 5 to 18, a reflectance of 40 to 80%, and an etching rate of 1.0 to50.0 μm/min with respect to inorganic acid; the phosphorous layers havea thickness of 10 to 50 μm; and a difference between the thermalexpansive coefficients of the dielectric layer and the barrier walllayer has a percentage between 0 and 10%, and a difference between thesoftening temperatures of the dielectric layer and the barrier walllayer has a value between 0 and 20° C.
 3. A rear plate of a plasmadisplay panel, the rear plate comprising: a glass substrate; electrodesformed in a shape of patterns on an upper surface of the glasssubstrate; a dielectric layer formed on upper surfaces of the electrodeand the upper surface of the glass substrate; barrier walls formed in ashape of a pattern through etching on an upper surface of the dielectriclayer; and phosphorous layers formed on side surfaces and bottomsurfaces of the barrier walls, wherein: the electrodes has a thicknessof 2 to 8 μm and a specific resistance of 1.0×10⁻⁶ to 5.0×10⁻⁶ Ωcm; thedielectric layer is made from a first mixture which includes a firstfiller, organic material, additives, and at least one glass powderselected from among a first glass powder and a second glass powder, thefirst glass powder including PbO of 30 to 80 wt %, ZnO of 0 to 20 wt %,SiO₂ of 0 to 20 wt %, B₂O₃ of 5 to 40 wt %, Al₂O₃ of 0 to 12 wt %,Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0 to 5 wt %, thesecond glass powder including Bi₂O₃ of 36 to 84 wt %, B₂O₃ of 5 to 28 wt%, PbO of 0 to 46 wt %, ZnO of 0 to 30 wt %, Al₂O₃ of 0 to 13 wt %, SiO₂of 0 to 10 wt %, Na₂O+K₂O+Li₂O of 0 to 5 wt %, and BaO+CaO+MgO+SrO of 0to 3 wt %, each of the first and second glass powders having an averageparticle diameter of 1 to 10 μm, a softening temperature of 390 to 550°C., and a thermal expansive coefficient of 63×10⁻⁷ to 83×10⁻⁷/° C., thefirst filler having an average particle diameter of 0.01 to 10 μm, thedielectric layer having a dielectric constant of 8 to 20, a reflectanceof 50 to 80%, an etching rate of 0.01 to 1.0 μm/min with respect toinorganic acid, and a thickness of 10 to 30 μm, the dielectric layerbeing formed in a shape of a green tape; the barrier walls are made froma second mixture which includes a second filler, organic material,additives, and at least one glass powder selected from the groupconsisting of a third, fourth, and fifth glass powders, the third glasspowder including ZnO of 0 to 48 wt %, SiO₂ of 0 to 21 wt %, B₂O₃ of 25to 56 wt %, Al₂O₃ of 0 to 12 wt %, Na₂O+K₂O+Li₂O of 0 to 38 wt %, andBaO+CaO+MgO+SrO of 0 to 15 wt %, the fourth glass powder including PbOof 25 to 65 wt %, ZnO of 0 to 35 wt %, SiO₂ of 0 to 26 wt %, B₂O₃ of 0to 30 wt %, Al₂O₃+SnO₂ of 0 to 13 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %,BaO of 0 to 26 wt %, and CaO+MgO+SrO of 0 to 13 wt %, the fifth glasspowder including PbO of 35 to 55 wt %, B₂O₃ of 18 to 25 wt %, ZnO of 0to 35 wt %, BaO of 0 to 16 wt %, SiO₂+Al₂O₃+SnO₂ of 0 to 9 wt %,CoO+CuO+MnO₂+Fe₂O₃ of 0 to 15 wt %, Na₂O+K₂O+Li₂O of 0 to 19 wt %, andCaO+MgO+SrO of 0 to 13 wt %, the third glass powder having a softeningtemperature of 460 to 630° C., a thermal expansive coefficient of64×10⁻⁷ to 105×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, each of the fourth and fifth glass powders having a softeningtemperature of 390 to 550° C., a thermal expansive coefficient of63×10⁻⁷ to 110×10⁻⁷/° C., and an average particle diameter of 0.5 to 17μm, the second filler having an average particle diameter of 0.01 to 10μm; the phosphorous layers have a thickness of 10 to 50 μm; and adifference between the thermal expansive coefficients of the dielectriclayer and the barrier wall layer has a percentage between 0 and 10%, anda difference between the softening temperatures of the dielectric layerand the barrier wall layer has a value between 0 and 20° C., wherein abarrier wall layer formed in a shape of green tapes, which has adielectric constant of 5 to 18, a reflectance of 40 to 80%, and anetching rate of 1.0 to 50.0 μm/min with respect to inorganic acid, isintegrated with the dielectric layer to form a lamination of dielectriclayer/barrier wall layer, and the lamination of dielectric layer/barrierwall layer is attached to the upper surfaces of the electrodes and theglass substrate, is baked at a temperature between 400° C. and 700° C.,and is then etched, so that the barrier walls are formed with a heightof 100 to 180 μm.
 4. A rear plate of a plasma display panel as claimedin any of claims 1 to 3, wherein each of the barrier walls has at leasttwo different layers having different etching rates with respect toinorganic acid.